1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly, to a mechanism for obtaining an orbital movement of a scroll member while preventing a rotation thereof about its own axis.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 59-28082 proposes a mechanism for obtaining an orbital movement in a scroll compressor, which includes a housing having a rotary scroll member housed therein A stationary ring and a rotary ring facing each other are arranged between the housing and the rotary scroll member at the facing sides thereof, respectively. Both rings form a plurality of opposite pairs of pockets and a tubular shaped bearing member arranged between the facing pockets. The arrangement is such that the radius of the orbital movement of the rotary scroll member is limited to the sum of the diameter of the movable area of the cylindrical bearing member in one of the opposite pockets and the diameter of the movable area of the cylindrical bearing member in the other pocket This orbital movement mechanism receives not only the thrust force in the rotary scroll member but also the radial force of the rotary scroll member, to prevent a rotation of the rotary scroll member about its own axis Accordingly, a compressor provided with this type of orbital movement mechanism has a simplified construction and requires a smaller number of parts when compared with a conventional type compressor provided with separate mechanisms for receiving the thrust force and for preventing self rotation.
In this type of improved mechanism for obtaining an orbital movement, an inclination of the cylindrical bearing member may occur due to displacement forces applied in opposite radial directions to the ends of the cylindrical bearing member during the orbital movement of the rotary scroll member, where a necessary precise degree of parallelism is not obtained between the end surfaces of the cylindrical bearing member. In this situation, the particular limited portions of the cylindrical bearing member, i.e., the edged portions at the ends of the member, can come into sliding contact with the corresponding housing and the rotary scroll member, which causes a partial wear of these parts after use for a very short period. Furthermore, even if the necessary precise degree of parallelism is obtained between the end surfaces of the cylindrical bearing member, wear and tear easily occurs during a very short period, based on the construction that the cylindrical bearing member is in partial contact, at the circumferential edge portions of the ends thereof, with the corresponding portions of the housing and the rotary scroll member. Due to this wear and tear, a clearance is generated between the inner surface of the base wall of the stationary scroll member and the tip end of the scroll portion of the stationary scroll member, thereby reducing the compression efficiency. Furthermore, the cylindrical bearing member is subjected to a reaction force caused by the compression at the portion near the outer periphery of the rotary scroll member, causing the base wall portion of the rotary scroll member to be bent. This brings the cylindrical bearing member into a greater partial contact with the rotary scroll member at the peripheral edge portions of the cylindrical bearing member, and thus wear and tear is very easily generated.